A new type optical disc whose data can be reproduced by a conventional CD-DA (Compact Disc Digital Audio) player and a CD-ROM (Compact Disc Read Only Memory) disc drive device and which is congenial with a computer has been developed. On the new type optical disc, content data is encrypted and recorded so as to protect copyright thereof. When content data is encrypted and recorded on the new type optical disc, key information for the content data is considered to be recorded in a lead-in area of the optical disc.
In other words, when content data is encrypted and recorded, it is necessary to consider a location at which the key information is stored. To securely manage the key information, it is advantageous to store the key information at a location which the user cannot easily access. Thus, when video data is recorded on for example a DVD (Digital Versatile Disc), key information is recorded in a lead-in area thereof and data encrypted with the key information is stored in a program area thereof. Likewise, for the new type optical disc, it is considered that key information should be recorded in a lead-in area thereof so that the user cannot easily access the key information.
When the DVD was designed, content data was considered to be encrypted so as to protect copyright thereof. Thus, when key information is recorded in the lead-in area, no problem takes place. However, if key information is recorded in the lead-in area of the new type optical disc, the conventional disc player and disc drive device which cannot deal with the new type optical disc will not be able to reproduce content data therefrom.
In other words, when the conventional CD-DA disc and CD-ROM disc were designed, content data was not considered to be encrypted. Thus, they do not have a function for decrypting encrypted content data. When the conventional disc player and disc drive device which cannot deal with the new type optical disc decrypt encrypted content data from the new type optical disc, a software process will be considered to perform a decrypting process for the content data.
However, while the conventional disc player and disc drive device are reproducing content data, the software does not allow them to access a lead-in area. In other words, corresponding to the CD-ROM standard, the CD-ROM is accessed in the unit of a sector which is composed of 98 frames. While the conventional disc player and disc drive device are reproducing content data from the CD-ROM, they access each sector, not the lead-in area of the CD-ROM. Thus, when key information has been recorded in the lead-in area, the conventional disc player and disc drive device which cannot deal with the new type optical disc cannot access the key information and thereby decrypt content data.
Of course, the disc player and disc drive device which can deal with the new type optical disc of which key information is recorded in the lead-in area will be designed to obtain the key information therefrom, and decrypt encrypted content data with the obtained key information. Thus, when the disc player and disc drive device have been widely used, the forgoing problem of which key information cannot be accessed from the lead-in area and content data cannot be reproduced will be solved.
However, in a transitional period until the disc player and disc drive device which can deal with the new type optical disc become common, the conventional disc player and disc drive device which cannot deal with the new type optical disc try to decrypt encrypted content data of the new type optical disc. Thus, since the conventional disc player and disc drive device cannot access key information of the lead-in area, they cannot decrypt the encrypted content data.
Therefore, an object of the present invention is to provide a recording medium and a recording medium recording method and apparatus which allow the conventional reproducing apparatus which cannot deal with encrypted content data to decrypt it.
Another object of the present invention is to provide a recording medium reproducing method and apparatus which allows the conventional apparatus which cannot deal with encrypted content data and an apparatus which can deal with encrypted content data to decrypt encrypted content data recorded on a recording medium.